Can there be more than Four Fundamental Forces?

We used to think gravity and electromagnetism were the two fundamental forces of nature until we discovered the strong and weak nuclear forces. Can we be wrong again and discover more forces. If not, then how are we so sure?

I don't know any physicist (especially cosmologist) who believes that 4 is the magic number of forces (although we usually call them interactions, or even more abstractly gauges - the term "force" is more to make contact with the laymen who have had a semester or two of physics). For example, SU(5) would be a single "force", but would manifest as, not only 3 of the 4 forces, but also leave many residuals.

You may be interested in a bit of history here, though. Perhaps the first recognized force was magnetism, thousands of years ago. Then, electrostatics and gravity (probably first electrostatics) were recognized, also in acient times. Interestingly, electricity and magnetism were once unified, but later separated by the wisdom of the scholars. Finally, electricity and magnetism were reunited in the nineteenth century. Then, there was the idea to unify gravity with electromagnetism using extra dimensions. That idea was put on hold, but recently it seems that extra dimensions (UED and/or SUSY) may be a viable candidate. Extra-dimensional theories are an example of theories that suggest phenomena that you could interpret as new kinds of "forces".

Interestingly, gravity remains to be the major obstacle to unification.

i think unable to find the inverse of the theories that we have made from the nature ,i.e. anti gravity theories, randomness theories make us to lead no where and finally we'll come to uncertainty theory and the things will be totally left out for experimental data!!

We used to think gravity and electromagnetism were the two fundamental forces of nature until we discovered the strong and weak nuclear forces. Can we be wrong again and discover more forces. If not, then how are we so sure?

Sure, there's no reason there couldn't be more forces. But they would probably have to act on scales much smaller than anything we can experimentally test now (otherwise they would have been discovered already).